With the release of iOS 13 comes some useful features; one of them is allowing third-party developers to release or update apps to access Siri without any configuration from the users' end. Before iOS 13, trying to set up a non-Apple app with Siri required setting up a Siri shortcut—and that didn't guarantee that it would work.
But as The Verge discovers two apps can now interface with Siri, somehow. And it'll help when it comes to driving. Siri now works with Google Maps and Waze, but some features still need to be worked on.
As The Verge's Jay Peters writes, "When I used general location requests—I tried 'the Apple Store' and 'Seattle'—Siri opened up Google Maps with directions ready. (I still had to tap the start button in the app, so it's not a completely hands-free experience.) But when I tried to ask Siri to give me directions to a few different numbered addresses in Google Maps, each time, my iPhone just opened Apple Maps instead. It appears it may need some tinkering, either from Apple or the app makers, to get third-party Siri support working as designed."
And one other thing you need to know is that you would need to tell Siri to open the specific app as a part of your command. You'll need to say things like "get me directions to Toronto in Waze." At the moment there's still no way to set a non-Apple app as a default for Siri like you can with Alexa or Google Assistant.